Conveyor systems

ABSTRACT

A power and free conveyor has a downwardly inclined section of its trolley track provided with a holding station at which is disposed a stop mechanism. The mechanism includes a stop arm which normally occupies an operative position in which it projects over the trolley track to depress into inoperative positions respective driving dogs and respective holdback dogs of trolleys on the track. In their operative positions, these driving dogs are engageable by pushers carried by an endless power chain running in a chain track spaced above the trolley track. The stop arm arrests a trolley by abutting the depressed holdback dog of the trolley. The mechanism also includes a second member which normally occupies an operative position in which it projects under the trolley track to restrain forward movement of a trolley at the holding station. On receipt of a signal from the next holding station along the track that the preceding trolley is clear of this next station, a pneumatic piston-and-cylinder device moves the stop arm into its inoperative position to cause a pusher to engage the driving dog of the detained trolley, and another such device allows the second member to move forwardly gradually into its inoperative position to cause a smooth forward movement of the trolley under the action of the pusher.

United States Patent- Hempstead Sept. 12, 1972 [54] CONVEYOR SYSTEMS [72] Inventor: Cyril Frank Hempstead, Stevenage,

England [73] Assignee: Geo W. King, Stevenage, England [22] Filed: May 24, 1971 21 Appl. No.1 146,323

[30] Foreign Application Priority Data Primary Examiner-Philip Arnold Attorney-Waters, Roditi, Schwartz & Nissen [57] ABSTRACT A power and free conveyor has a downwardly inclined section of its trolley track provided with a holding station at which is disposed a stop mechanism. The mechanism includes a stop arm which normally occupies an operative position in which it projects over the trolley track to depress into inoperative positions respective driving dogs and respective holdback dogs of trolleys on the track. In their operative positions, these driving dogs are engageable by pushers carried by an endless power chain running in a chain track spaced above the trolley track. The stop arm arrests a trolley by abutting the depressed holdback dog of the trolley. The mechanism also includes a second member which normally occupies an operative position in which it projects under the trolley track to restrain forward movement of a trolley at the holding station. On receipt of a signal from the next holding station along the track that the preceding trolley is clear of this next station, a pneumatic piston-andcylinder device moves the stop arm into its inoperative position to cause a pusher to engage the driving dog of the detained trolley, and another such device allows the second member to move forwardly gradually into its inoperative position to cause a smooth forward movement of the trolley under the action of the pusher.

8 Claims, 5 Drawing Figures PATENTEDsEP 1; I972 SHEET 1 [IF 4 PATENTEDsEP 12 I972 SHEET 2 0F 4 Mum P'A'TENTEDSEPIZIFJYZ 3.690.269 sums 0F 4 FIG.34.

1 CONVEYOR SYSTEMS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention is concerned with a power and free conveyor, wherein load-carrying trolleys are propelled along a fixed trolley track by virtue of the engagement therewith of pushers which depend from an endless driven chain arranged to travel along a path above the trolley track.

2. Description of the Prior Art In such power and free conveyors it is frequently necessary to incorporate vertical bends to change the level of the conveyor, forexample, from one floor of a building to anothenFurthermore it is frequently necessary, particularly in the case of storage conveyors, to fit at spaced pointsalong the conveyor path indexing statiOn'sjwhich are operative to holdup the flow of load trolleys and to release them singly as required; Such an indexing station is disclosed in British Pat. specification No. 1105760.- 1 i I With self indexing or soecalled proximity type trolleys itis'irnportant to ensure that the leading load trolley will have cleared the foremost indexing or'holding station or auto stop on a down slope before the next load trolley is released from the preceding indexing station in order to avoid uncontrolled self-indexing down an inclined section of thetrolley track.

It is alsovaluable to ensure that a detained trolley is moved forward smoothly from an indexing station to avoid jerking and swinging of the load, as tends to occur in the conveyor disclosed in the aforesaid British patentspecification.

SUMMARY OF THE INVENTION According to the present invention, there is provided a power and free conveyor, comprising a trolley track having a downwardly inclined section, load-carrying trolleys mountedon the track for moving therealong, an endless power chain having a part extending along said track and upwardly spaced from said track for driving said trolleys in one direction along said track, driving dogs on the respective trolleys movable between respective operative and inoperative positions, pushers on the chain serving to engage said driving dogs, while said driving dogs are in their operative positions, to move said trolleys along said track in said direction, a stop mechanism disposed at a holding station on said downwardly inclined section, a first member of said mechanism movable between a normally occupied operative position, in which it extends above said track and is effective to move the driving dog of an approaching trolley into an inoperative position, and an inoperative position, in which it lies out of the path of movement of such driving dog, a second member of said mechanism movable between a normally occupied operative position, in which it extends below said track and is efiective to restrain movement of such approaching trolley in said direction, and an inoperative position, in which it lies out of the path of movement of such trolley, means operative on receipt of a signal from a point forwardly of said holding station to cause movement of said first member into said inoperative position of said first member to allow the driving dog of the trolley detained by said mechanism to move into its operative position, and to cause also a controlled movement of said second member into said inoperative position of said second member to allow a trolley detained by said mechanism to be moved smoothly from said holding station.

BRIEF DESCRIPTION OF THE DRAWING For a better understanding of the invention reference will now be made to the accompanying drawings in which: a

FIG. 1 is a perspective view showing a small portion of a conveyor of the kind with which the invention is concerned, certain parts being broken away to permit ofbetter illustration,

FIG. 2 is a side elevation view of a stop mechanism forming an example in accordance with the invention,

FIG. 3 is a plan view of the mechanism shown in FIG.

FIG. 4 is a sectional view taken on the line A-A of FIG.3,

FIG. 5 shows diagrammatically one possibleform of control system for the mechanism shown inFIGS. 2-4.

' DESCRIPTION oFTHE PREFERRED EMBODIMENT Referring now to FIG. 1 which illustrates diagrammatically a small section of a conveyor of the kind with which the invention is concerned, l0 denotes a load carrying trolley which is equipped with a depending load bar 11 from which loads to be conveyed are suspended. Load carrying trolleys such as that indicated at v10 are propelled along a fixed track 12, hereinafter termed the trolley track, by means of an endless driven chain 13 which is supported at spaced points along its lengthby'means of so-called chain trolleys one of which is indicated at 14. The chain trolleys run on a second fixed track 16, hereinafter termed the chain trolley track, disposed vertically above the track 12. The chain 13 is provided at spaced points along its length with depending pusher dogs '17 which are adapted to cooperate with upstanding driving abutments on the load carrying trolleys 10, the arrangement being such that on a drive being imparted to the chain 13 the dogs 17 will by virtue of their engagement with the abutrnents on the trolleys 10 cause the latter to be propelled along the track 12. In the embodiment illustrated l8 denotes the driving abutment on the trolley 10.

In known manner each trolley is equipped with an upstanding retainer abutment 19 which will be effective to prevent uncontrolled forward movement of said trolleys relatively to chain 13. To allow for indexing of load trolleys, i.e., for stoppage of such trolleys at one or more selected points along the conveyor path without any interruption of the drive to the chain 13, the drive abutment 18 on each trolley is so mounted as to be capable .of retraction into a position wherein it will lie out of the path of the pusher dogs 17 on the chain. The retainer abutment 19 on each trolley 10 is so mounted that while being free to pivot forwardly, i.e., in the direction of travel of the trolley it will be held against movement past the vertical position in a rearward direction. As indicated conveyors of the kind generally indicated above are well known and further description thereof is not considered necessary.

Referring now to FIGS. 2-4, which show a stop mechanism suitable for installation on a downwardly inclined section of a conveyor of the kind above referred to, 20 denotes a stop arm which is normally urged by means of a spring 200, encircling a guide rod 20b, into its operative position wherein as clearly shown in FIG. 4 it will project across the top of the trolley track 12, so that it will lie in the path of the depressible drive abutment 18 on any trolley approaching the stop mechanism. The stop arm 20 is slidable in a guide 21 and is retractable into an inoperative position on operation of an air cylinder 22 the piston rod 23 of which is coupled to an upstanding projection 24 fixedly mounted on the stop arm 20. In addition to the stop arm 20 a further stop member. 25 is provided which as can be seen from FIG. 4 is'disposed below the trolley track 12 so as to lie in the path of the body of any load trolley approaching the stop mechanism. The member 25 is pivotally mounted at 26 between two guideplates 27 and 28 which are fitted with four rollers 29 adapted to engage and roll ona fixed guide plate 30 which extends parallel to the trolley track 12. Mounted on the member 25 is a guide roller 31 which is adapted to cooperate with a fixed guide 32, the latter as can be seen from FIG. 3 including a portion which is parallel to the trolley track 12 and a portion 32a which is inclined outwardly or away from said track. Connected to a bracket at the underside of the lower guide plate 28 is the ram of a second air cylinder 33 by means of which the guide plates 27 and 28 and the member 25 may be moved from an initial, left-hand position shown in FIG. 3 to a right-hand position as shown in chain lines and vice versa.

In FIG. a suitable control system is illustrated by way of example and the operation of the mechanism above described will be as follows, it being understood that such mechanism is installed on a downwardly inclined section of the load trolley track 12.

With the stop arm in its operative position any load trolley arriving at the stop mechanism will have its drive abutment 18 depressed by said stop arm so that such abutment will then be out of the path of the depending pusher dogs 17 on the endless driven chain of the conveyor. Owing to an interlocking action between the abutment 18 and the retainer dog 19 on the load trolley, as described in the specification of our prior Patent Application No. 44356/69, the retainer dog 19, which owing to the downward inclination of the track will have been in contact with a pusher dog 17, will also be depressed out of the path of the pusher dogs, but the arrangement is such that at this point the forward end of the load trolley body will abut the member 25 which extends across the underside of the trolley track 12. As indicated above, the member 25 is effectively controlled by the air cylinder 33 in which the air pressure is regulated by means of a balance valve 34 (FIG. 5) to a pressure which will allow the member 25 to move forward slightly as a result of the pressure exerted by the load trolley and the load carried thereby. The load trolley will move forwardly against the member 25 until it is arrested as a result of the abutment against the stop arm 20 of a projection on the top of one of the side plates of the load trolley. The load trolley is at that stage positively prevented from running forwardly down the inclined track 12 and the dogs on the endless driven chain will travel freely over the top of the trolley the drive abutment 18 of which is still held down by the stop arm 20 with resultant continued depression of the retaining dog 19.

When a signal is received that the preceding load trolley (i.e., the load trolley ahead of the one held by the mechanism) is clear of the next forward stop, the cylinder 22 will be operated to retract the stop arm 20 so that the load trolley will bear fully on the member 25. As a result of withdrawal of the stop arm 20 the drive abutment 18 will rise again into its operative position wherein it will be contacted by the next depending pusher dog on the endless driven chain. As a result of the drive thus then imparted to the load trolley the member 25 will be pushed by the trolley in a forward direction against the preset pressure in the cylinder 33 and will commence to pivot sideways such movement being allowed by virtue of the fact that the guide roller 31 will then be in contact with the portion 32a of the fixed guide 32. The arrangement is such that when the member 25 has travelled a short distance it will contact a valve 35 which will cause air to be fed into the other end of the cylinder 33 via a valve 36. The exhaust from the rear end of the cylinder 33 is controlled by a restrictor valve 37 which allows the cylinder to push the member 25 forwardly at a slightly greater speed then that at which the endless driven chain of the conveyor is travelling. As the load trolley is still in contact with the member 25 it will travel forwardly until the trolley retainer dog 19 comes into contact with the depending pusher dog on the endless driven chain, so that any sudden jerk forwardly on to such dog will be obviated when the member 25 has pivoted sufficiently to release the load trolley.

When the load trolley is clear of the stop mechanism the member 25 will be reset to its original position as a result of appropriate activation of the cylinder 33 resultant upon operation of an air valve 38. The stop arm 20 will be returned to its initial operative position by means of its return spring 20a when an air valve is operated by the retainer dog on the trolley as it passes out of the stop mechanism. The stop mechanism will thus be reset to hold the next following load trolley until the load trolley that has just left the stop mechanism has been released from the next station ahead.

I claim:

1. A power and free conveyor, comprising a trolley track having a downwardly inclined section, load-carrying trolleys mounted on the track for moving therealong, an endless power chain having a part extending along said track and upwardly spaced from said track for driving said trolleys in one direction along said track, driving dogs on the respective trolleys movable between respective operative and inoperative positions, pushers on the chain serving to engage said driving dogs, while said driving dogs are in their operative positions, to move said trolleys along said track in said direction, a stop mechanism disposed at a holding station on said downwardly inclined section, a first member of said mechanism movable between a normally occupied operative position, in which it extends above said track and is effective to move the driving dog of an approaching trolley into an inoperative position, and an inoperative position, in which it lies out of the path of movement of such driving dog, a second member of said mechanism movable between a normally occupied operative position, in which it extends below said track and is effective to restrain movement of such approaching trolley in said direction, and an inoperative position, in which it lies out of the path of movement of such trolley, means operative on receipt of a signal from a point forwardly of said holding station to cause movement of said first member into said inoperative position of said first member to allow the driving dog of the trolley detained by said mechanism to move into its operative position, and to cause also a controlled movement of said second member into said inoperative position of said second member to allow a trolley detained by said mechanism to be moved smoothly from said holding station.

2. A conveyor according to claim 1, wherein said means comprises a fluid pressure circuit containing a fluid-pressure actuated .piston-and-cylinder device which is connected to said second member and the fluid pressure in which serves to counteract partially the driving force of a pusher on the driving dog of a trolley restrained by said second member.

3. A conveyor according to claim 1, wherein said stop mechanism comprises a drive device which is connected to said second member and which serves to counteract partially the driving force of a pusher on the driving dog of a trolley retained by said second member, means mounting said second member such that said second member is swingable between its operative position and its inoperative position, and guide means which guides movement of said second member between its operative position and its inoperative position and which comprises a first guide part which maintains said second member in its operative position in said path of movement of such trolley and a second guide part which controls swinging of said second member from its operative position into its inoperative position.

4. A conveyor according to claim 3, wherein said second member is a cranked arm which is supported at from said path of movement of such trolley, and said cranked arm being mounted at said mounting means by way of one end of said cranked arm such that said one end is nearer said approaching trolley than is said cranked portion.

5. A conveyor according to claim 3, wherein said mounting means comprises a slide, and said slide is mounted on a guide for reciprocation substantially parallel to said path of movement of such trolley.

6. A conveyor according to claim 2, wherein said circuit also comprises a restrictor which is connected downstream of said device with respect to fluid displacement in said circuit during movement of said second member from its operative position to its inoperative position and which allows only controlled movement of the piston of said device during this movement of said second member.

7. A conveyor according to claim 2, wherein said circuit also comprises a double-acting pneumatic changeover valye which is connected to said device, wherein said device is double-acting and is controlled by said change-over valve, and wherein said change-over valve is controlled by firstand second pneumatic valves.

8. A conveyor according to claim 7, wherein, during movement of said trolley restrained by said second member under said driving force of a pusher and well before said second member attains its inoperative position, said first pneumatic valve changes over said change-over valve from supplying fluid to said device to urge movement of said second member from its operative position to its inoperative position to supplying fluid to said device to urge movement of said second member from its inoperative position to its operative position. 

1. A power and free conveyor, comprising a trolley track having a downwardly inclined section, load-carrying trolleys mounted on the track for moving therealong, an endless power chain having a part extending along said track and upwardly spaced from said track for driving said trolleys in one direction along said track, driving dogs on the respective trolleys movable between respective operative and inoperative positions, pushers on the chain serving to engage said driving dogs, while said driving dogs are in their operative positions, to move said trolleys along said track in said direction, a stop mechanism disposed at a holding station on said downwardly inclined section, a first member of said mechanism movable between a normally occupied operative position, in which it extends above said track and is effective to move the driving dog of an approaching trolley into an inoperative position, and an inoperative position, in which it lies out of the path of movement of such driving dog, a second member of said mechanism movable between a normally occupied operative position, in which it extends below said track and is effective to restrain movement of such approaching trolley in said direction, and an inoperative position, in which it lies out of the path of movement of such trolley, means operative on receipt of a signal from a point forwardly of said holding station to cause movement of said first member into said inoperative position of said first member to allow the driving dog of the trolley detained by said mechanism to move into its operative position, and to cause also a controlled movement of said second member into said inoperative position of said second member to allow a trolley detained by said mechanism to be moved smoothly from said holding station.
 2. A conveyor according to claim 1, wherein said means comprises a fluid pressure circuit containing a fluid-pressure actuated piston-and-cylinder device which is connected to said second member and the fluid pressure in which serves to counteract Partially the driving force of a pusher on the driving dog of a trolley restrained by said second member.
 3. A conveyor according to claim 1, wherein said stop mechanism comprises a drive device which is connected to said second member and which serves to counteract partially the driving force of a pusher on the driving dog of a trolley retained by said second member, means mounting said second member such that said second member is swingable between its operative position and its inoperative position, and guide means which guides movement of said second member between its operative position and its inoperative position and which comprises a first guide part which maintains said second member in its operative position in said path of movement of such trolley and a second guide part which controls swinging of said second member from its operative position into its inoperative position.
 4. A conveyor according to claim 3, wherein said second member is a cranked arm which is supported at its cranked portion by said guide means, said first guide part having a guide surface substantially parallel to said path of movement of such trolley, said second guide part having a guide surface inclined obliquely away from said path of movement of such trolley, and said cranked arm being mounted at said mounting means by way of one end of said cranked arm such that said one end is nearer said approaching trolley than is said cranked portion.
 5. A conveyor according to claim 3, wherein said mounting means comprises a slide, and said slide is mounted on a guide for reciprocation substantially parallel to said path of movement of such trolley.
 6. A conveyor according to claim 2, wherein said circuit also comprises a restrictor which is connected downstream of said device with respect to fluid displacement in said circuit during movement of said second member from its operative position to its inoperative position and which allows only controlled movement of the piston of said device during this movement of said second member.
 7. A conveyor according to claim 2, wherein said circuit also comprises a double-acting pneumatic change-over valve which is connected to said device, wherein said device is double-acting and is controlled by said change-over valve, and wherein said change-over valve is controlled by first and second pneumatic valves.
 8. A conveyor according to claim 7, wherein, during movement of said trolley restrained by said second member under said driving force of a pusher and well before said second member attains its inoperative position, said first pneumatic valve changes over said change-over valve from supplying fluid to said device to urge movement of said second member from its operative position to its inoperative position to supplying fluid to said device to urge movement of said second member from its inoperative position to its operative position. 